1. Field of the Invention
Embodiments of the present invention generally relate to testing electronic components, and more specifically to testing magnetoresistive heads.
2. Description of the Related Art
Magnetic disk drive based systems have been widely accepted in the computer industry as a cost-effective form of data storage. In a magnetic disk drive system, a magnetic recording medium in the form of a disk rotates at high speed while a magnetic head “flies” slightly above the surface of the rotating disk. The magnetic disk is rotated by means of a spindle drive motor. The magnetic head is attached to or formed integrally with a “slider” which is suspended over the disk by a suspension assembly, which in turn is attached to an actuator arm. As the magnetic disk rotates at an operating speed, the moving air generated by the rotating disk in conjunction with the physical design of the slider lifts the magnetic head, allowing it to glide or “fly” slightly above and over the disk surface on a cushion of air, referred to as an air bearing.
Magnetoresistive (MR) sensors are particularly useful as read elements in magnetic heads, used in the data storage industry for high data recording densities. Examples of MR materials used in the storage industry include anisotropic magnetoresistive (AMR), giant magnetoresistive (GMR), and tunneling magnetoresistive (TMR). MR sensors are deposited as small and thin multi-layered sheet resistors on a structural substrate. The sheet resistors can be coupled to external devices by contact to metal pads which are electrically connected to the sheet resistors.
To achieve the high areal densities required by the data storage industry, the sensors are made with commensurately smaller dimensions. The smaller the dimensions, the more sensitive the thin sheet resistors become to damage from spurious current or voltage spikes during fabrication. Furthermore, the likelihood that fabrication defects will adversely affect the performance of the magnetic heads is greater with relatively smaller dimensions. While fabricating a plurality of substantially similar magnetic heads simultaneously on the same wafer, fabrication defects may occur in one or more of the plurality of magnetic heads. Another significant cause of defects may be intrinsic variations in the orientation of crystals used to form the magnetic head and/or regions around it. Accordingly, it is not uncommon to test the magnetic heads after fabrication to identify defective magnetic heads.